Journal articles: 'Dolomite - South Africa'

1

Wagener, Fritz Von M., and Peter W. Day. "Construction on dolomite in south Africa." Environmental Geology and Water Sciences 8, no. 1-2 (March 1986): 83–89. http://dx.doi.org/10.1007/bf02525561.

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2

Van Tonder, G. J., J. F. Botha, and F. Wiegmans. "The use of kriging in gravity-surveys." Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 4, no. 1 (March 18, 1985): 25–28. http://dx.doi.org/10.4102/satnt.v4i1.1014.

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The present investigation is mostly concerned with the contribution that kriging can make towards reducing the number of observed gravity measurements necessary for a reliable estimate of the volume weathered dolomite in the dolomitic areas of South Africa. After a brief introduction, the method is applied to the Bouguer anomaly values of a part of the Zuurbekom Compartment. It is shown that by using kriging, the number of measuring stations can be reduced by op to 90 percent without affecting the accuracy of the calculation of the estimated volume of the weathered dolomite adversely.

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Dawson, J. B., and R. W. Hinton. "Trace-element content and partitioning in calcite, dolomite and apatite in carbonatite, Phalaborwa, South Africa." Mineralogical Magazine 67, no. 5 (October 2003): 921–30. http://dx.doi.org/10.1180/0026461036750151.

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AbstractA carbonatite sample from Phalaborwa, South Africa, consists of apatite, magnetite and a calcitedolomite ‘perthite’ which is interpreted as being due to exsolution of dolomite from a high-Mg calcite precursor. Carbon and oxygen isotope data indicate that the carbonates are equilibrated. In situ ionmicroprobe analyses for Fe, Mn, Na, Si, Y, the REEs, Pb, Th and U give the following average concentrations (in ppm) in the sequence apatite, calcite, dolomite: Fe 98, 1680, 8190; Mn 61, 510, 615; Na 1171, 627, 125; Si 368; 1.6, 0.2; Sr 4447, 5418, 2393; Ba 37, 2189, 75; La 1245, 300, 67; Y 121, 50, 5.8; Pb 16, 5.4, 1.4; Th 20, 0.02, 0; U 2.4, 0, 0.01. The concentrations are reasonably uniform in both apatite and dolomite, but in calcite are more variable. Na, Si, Y, the REEs, Pb, Th and U partition into apatite relative to both carbonates (and, hence, the precursor carbonate); KD ap/cc for REE decreases from ∽4 for La to ∽2 for Tm. There is almost equal partitioning of Sr between apatite and calcite. During separation of dolomite from calcite, Sr and Ba partition strongly into calcite and all the other analysed elements, except Fe and Mn, also preferentially enter calcite. The REEs prefer calcite relative to dolomite, and the KD dol/cc is reasonably constant, only varying from 0.23 to 0.17. Sr, Ba and Pb in the carbonates, and their partitioning between the calcite and dolomite, differ from other carbonatite carbonates reported in the literature.

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Swart, D., M. A. Dippenaar, and J. L. Van Rooy. "Mechanical and hydraulic properties of residual dolomite and wad." South African Journal of Geology 122, no. 3 (September 1, 2019): 379–88. http://dx.doi.org/10.25131/sajg.122.0024.

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Abstract The properties of residual dolomite, sometimes termed wad, are variable and uncertain. It represents the insoluble residue after dissolution of dolomite and is commonly found in the Neoarchaean Malmani Subgroup of the Chuniespoort Group (South Africa). This study comprised triaxial tests, crumb tests, X-Ray diffraction and fluorescence spectroscopy, foundation indicators, stereo-microscope imagery and permeability testing of the represented formations outcropping in the northeastern portions of South Africa. Results concur that residual dolomite is not typically dispersive, has low density that can be below that of water, mostly grades in the silt fraction, has high plasticity indices with low to high liquid limits, and has hydraulic conductivities in the order of 1x10-6 m/s. This new knowledge database contributes to our understanding of the flow through these systems and to how ingress scenario subsidences and sinkholes can possibly occur.

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5

van Schalkwyk, A. "Legal aspects of development on dolomite land in South Africa." Environmental Geology 36, no. 1-2 (November 20, 1998): 167–69. http://dx.doi.org/10.1007/s002540050332.

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6

De Bruyn, I. A., and F. G. Bell. "The occurrence of sinkholes and subsidence depressions in the far west Rand and Gauteng Province, South Africa, and their engineering implications." Environmental and Engineering Geoscience 7, no. 3 (August 1, 2001): 281–95. http://dx.doi.org/10.2113/gseegeosci.7.3.281.

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Abstract Dewatering associated with mining in the gold-bearing reefs of the Far West Rand, which underlie dolomite and unconsolidated deposits, led to the formation of sinkholes and subsidence depressions. Hence, certain areas became unsafe for occupation and were evacuated. Although sinkholes were initially noticed in the 1950s, the seriousness of the situation was highlighted in December 1962 when a sinkhole engulfed a three-story crusher plant at West Driefontein Mine. Consequently, it became a matter of urgency that the areas at risk of subsidence and the occurrence of sinkholes were delineated. Sink-holes formed concurrently with the lowering of the water table in areas which formerly had been relatively free of sinkholes. In addition, subsidence occurred as a consequence of consolidation taking place in the unconsolidated deposits as the water table was lowered. In the latter case, the degree of subsidence which occurred reflected the thickness and original density of the unconsolidated deposits which were consolidated. These deposits vary laterally in thickness and thereby gave rise to differential subsidence. Subsidence also occurred due to the closure of dewatered voids at the rock-soil interface. The risk of sinkhole and subsidence occurrence is increased by urban development, since interrupted natural surface drainage, increased runoff, and leakage from water-bearing utilities can result in the concentrated ingress of water into the ground. Where the surficial deposits are less permeable, the risk of instability is reduced. In the area underlain by dolomite, which extends around Johannesburg and Pretoria, these problem have been more notable in recent years because of housing development, both low-cost and up-market, and the growth of informal settlements. Residential densities may be very high, especially for low-cost housing, the development of which frequently has proceeded without recognition of the risk posed by karst-related ground instability. The appearance of significant numbers of small sinkholes has been associated with dolomite at shallow depth, that is, occurring at less than 15 m beneath the ground surface. The vulnerability of an area overlying dolomite bedrock at shallow depth is largely dependent on the spacing, width and continuity of grikes. When dolomite is located at depths greater than 15 m, the sinkholes which appear at the surface usually are larger in diameter. The risk of sinkhole occurrence in areas of shallow dolomite in general, may be greater, although the hazard itself is less severe. A classification system for the evaluation of dolomitic land based on the risk of formation of certain sized sinkholes has enabled such land to be zoned for appropriate development. Ongoing monitoring and maintenance of water bearing services, and the implementation of precautionary measures relating to drainage and infiltration of surface water are regarded as essential in developed areas underlain by dolomite. Special types of foundation construction for structures are frequently necessary.

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7

Mndaweni, S. S. E., S. Naicker, and D. Blake. "Hydrostratigraphy of the Malmani Subgroup dolomites within the northeastern escarpment (Limpopo and Mpumalanga, South Africa)." South African Journal of Geology 122, no. 3 (September 1, 2019): 283–98. http://dx.doi.org/10.25131/sajg.122.0022.

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Abstract The Late Archaean to Early Proterozoic Malmani Subgroup comprises of dolomites and limestones forming part of the Chuniespoort Group within the Transvaal Supergroup, outcropping as an arc structure east of the Pretoria Group along the Limpopo and Mpumalanga escarpment. These rocks form a fractured karst aquifer in the area and have a high degree of heterogeneity and anisotropy. The aquifers are unconfined to semi-confined, with compartmentalisation by dolerite dykes being a possible effect (if the dykes are large and extensive enough) due to the dykes acting as aquitards or barriers to groundwater flow. The contact zones between the dolomite formations and dolerite dykes are usually fractured however, and along with any other faults and fractures result in preferential dolomite dissolution and the development of groundwater flow paths in the area. Borehole yields ranges between 2 to 5 l/s and potentially >10 l/s per borehole in the vicinity of large regional fractures or dolerite intrusions. Groundwater from the Malmani Subgroup generally meets the drinking water quality standards for major constituents and it is of Mg-Ca-HCO3 nature. Groundwater development within this particular hydrostratigraphy is linked to potential well field target zones that take cognisance of various surface water-groundwater interaction affecting surface water discharge rates as well as groundwater over-abstraction concerns. Preliminary results have indicated that given a groundwater potential of 44 hm3/a, the aquifer will be able to support abstractions of up to 29 hm3/a if systematically developed adaptively and could be used and managed conjunctively with surface water to alleviate the pressure on the already stressed Olifants Water Management Area.

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8

Jonker, B., and T. Abiye. "Groundwater potential of the eastern Kalahari region of South Africa." South African Journal of Geology 120, no. 3 (September 1, 2017): 385–402. http://dx.doi.org/10.25131/gssajg.120.3.385.

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Abstract An integrated approach involving geological, borehole data, hydrogeochemical and environmental isotope analyses was used to determine the groundwater potential of the eastern Kalahari region of South Africa, an area to the west of Mahikeng that stretches northward from the Orange River into Botswana. The total groundwater resource potential for the eastern Kalahari region of South Africa is estimated at 10127 Mm3/a, with the Kalahari Group aquifer showing the greatest potential, comprising 51% of the total resource. The storage capacity of the Kalahari Group aquifer (7130 Mm3) is also impressive, estimated to be more than twice that of the dolomite aquifer (2728 Mm3). Despite having such great potential, the aquifer is not actively recharged and is often associated with very saline water that is not suitable for human and livestock consumption. The limestone and dolomite aquifers of the Campbell Rand Subgroup, as well as the weathered granitic rocks of the Archaean basement, are considered as the most prospective water bearing formations, with a groundwater resource potential estimate of 1981 Mm3/a and 1845 Mm3/a, respectively. Aquifers with the least potential in the project area comprise the fractured basement rocks of the Kraaipan - Amalia greenstone belt, with a groundwater resource potential of 26 Mm3/a, and the fractured sedimentary rocks of the Asbestos Hills Subgroup, with a groundwater resource potential of 108 Mm3/a. The calculated groundwater storage and resource potential in the eastern Kalahari region of South Africa satisfies a large proportion of the water demand in the region.

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9

MAUGER, CARLA L., and JOHN S. COMPTON. "Formation of modern dolomite in hypersaline pans of the Western Cape, South Africa." Sedimentology 58, no. 7 (April 5, 2011): 1678–92. http://dx.doi.org/10.1111/j.1365-3091.2011.01229.x.

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10

Swart, C. J. U., and A. van Schalkwyk. "Subsurface grout barriers for ground stabilization in dolomite areas near Carletonville, South Africa." Environmental Geology 40, no. 4-5 (February 7, 2001): 592–601. http://dx.doi.org/10.1007/s002540000222.

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11

Buttrick, D., and A. van Schalkwyk. "Hazard and risk assessment for sinkhole formation on dolomite land in South Africa." Environmental Geology 36, no. 1-2 (November 20, 1998): 170–78. http://dx.doi.org/10.1007/s002540050333.

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12

Botha, G. A., and J. C. Hughes. "Pedogenic palygorskite and dolomite in a late Neogene sedimentary succession, northwestern Transvaal, South Africa." Geoderma 53, no. 1-2 (May 1992): 139–54. http://dx.doi.org/10.1016/0016-7061(92)90027-5.

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13

Xiao, Liang, Yongxin Xu, and A. S. Talma. "Hydrochemical and isotopic approach to dynamic recharge of a dolomite aquifer in South Africa." Hydrogeology Journal 27, no. 3 (March 5, 2019): 945–64. http://dx.doi.org/10.1007/s10040-019-01926-z.

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14

Kafri, U., and M. B. J. Foster. "Hydrogeology of the malmani dolomite in the Klip River and Natalspruit basins, South Africa." Environmental Geology and Water Sciences 13, no. 2 (March 1989): 153–66. http://dx.doi.org/10.1007/bf01664700.

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15

Bezuidenhout, H., G. J. Bredenkamp, and G. K. Theron. "A classification of the vegetation of the western Transvaal dolomite and chert grassland, South Africa." South African Journal of Botany 60, no. 3 (June 1994): 152–61. http://dx.doi.org/10.1016/s0254-6299(16)30626-3.

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16

Potgieter, Abraham S., Stephanus J. Pretorius, and Izak Jacobus Van Der Walt. "Integration of a Dolomite Risk Management Programme in Local Governance in South Africa: Tlokwe City Council." Journal of Environmental Protection 07, no. 07 (2016): 1041–49. http://dx.doi.org/10.4236/jep.2016.77092.

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17

Harmer, R. E. "Evidence for magmatic crystallisation of ferroan dolomite at shallow depths in the Bulhoek Carbonatite Complex, South Africa." Journal of African Earth Sciences 32, no. 1 (January 2001): A18—A19. http://dx.doi.org/10.1016/s0899-5362(01)90038-7.

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18

Jahn, Bor-ming, and Bruce M. Simonson. "Carbonate PbPb ages of the Wittenoom Formation and Carawine Dolomite, Hamersley Basin, Western Australia (with implications for their correlation with the Transvaal Dolomite of South Africa)." Precambrian Research 72, no. 3-4 (April 1995): 247–61. http://dx.doi.org/10.1016/0301-9268(94)00092-6.

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19

Dowding, C. E., and M. V. Fey. "Morphological, chemical and mineralogical properties of some manganese-rich oxisols derived from dolomite in Mpumalanga province, South Africa." Geoderma 141, no. 1-2 (September 2007): 23–33. http://dx.doi.org/10.1016/j.geoderma.2007.04.024.

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20

Herries, Andy I. R., Justin W. Adams, Renaud Joannes-Boyau, Brian Armstrong, Stephanie Baker, Alex F. Blackwood, Giovanni Boschian, et al. "Integrating palaeocaves into palaeolandscapes: An analysis of cave levels and karstification history across the Gauteng Malmani dolomite, South Africa." Quaternary Science Reviews 220 (September 2019): 310–34. http://dx.doi.org/10.1016/j.quascirev.2017.02.007.

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21

Kleinhans, Ilse, and J. Louis Van Rooy. "Guidelines for sinkhole and subsidence rehabilitation based on generic geological models of a dolomite environment on the East Rand, South Africa." Journal of African Earth Sciences 117 (May 2016): 86–101. http://dx.doi.org/10.1016/j.jafrearsci.2016.01.001.

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22

Jahn, Bor-ming, J. Bertrand-Sarfati, N. Morin, and J. Macé. "Direct dating of stromatolitic carbonates from the Schmidtsdrif Formation (Transvaal Dolomite), South Africa, with implications on the age of the Ventersdorp Supergroup." Geology 18, no. 12 (1990): 1211. http://dx.doi.org/10.1130/0091-7613(1990)018<1211:ddoscf>2.3.co;2.

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23

F., Calitz. "Evaluation of the risk of the formation of karst-related surface instability features in dolomite strata occurring in the Lebowakgomo area, Republic of South Africa." Environmental Geology 42, no. 5 (August 1, 2002): 499–504. http://dx.doi.org/10.1007/s00254-001-0511-x.

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Leketa, Khahliso, and Tamiru Abiye. "Using Environmental Tracers to Characterize Groundwater Flow Mechanisms in the Fractured Crystalline and Karst Aquifers in Upper Crocodile River Basin, Johannesburg, South Africa." Hydrology 8, no. 1 (March 19, 2021): 50. http://dx.doi.org/10.3390/hydrology8010050.

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Environmental isotope tracers were applied in the Upper Crocodile River Basin, Johannesburg, South Africa, to understand the groundwater recharge conditions, flow mechanisms and interactions between surface and subsurface water. Stable isotope analysis indicated that recharge into the fractured quartzite aquifer occurs through direct mechanisms. The high variability in the stable isotope signature of temporal samples from Albert Farm spring indicated the importance of multiple samples for groundwater characterization, and that using a single sample may be yielding biased conclusions. The observed inverse relationship between spring discharge and isotope signature indicated the traces of rainfall amount effect during recharge, thereby suggesting piston groundwater flow. It is deduced that a measured discharge value can be used in this relationship to calculate the isotopic signature, which resembles effective rainfall. In the shallow alluvial deposits that overlie the granitic bed-rock, piezometer levels and stable isotopes revealed an interaction between Montgomery stream and interflow, which regulates streamflow throughout the year. This suggests that caution should be taken where hydrograph separation is applied for baseflow estimates, because the stream flow that overlies such geology may include significant interflow. The hydrochemistry evolution was observed in a stream fed by karst springs. As pH rises due to CO2 degassing, CaCO3 precipitates, thereby forming travertine moulds. The values of saturation indices that were greater than zero in all samples indicated supersaturation by calcite and dolomite and hence precipitation. Through 14C analysis, groundwater flow rate in the karst aquifer was estimated as 11 km/year, suggesting deep circulation in karst structures.

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Akintola, George Oluwole, Francis Amponsah-Dacosta, Steven Rupprecht, Nithyadharseni Palaniyandy, Sphiwe Emmanuel Mhlongo, Wilson Mugera Gitari, and Joshua Nosa Edokpayi. "Methanogenesis Potentials: Insights from Mineralogical Diagenesis, SEM and FTIR Features of the Permian Mikambeni Shale of the Tuli Basin, Limpopo Province of South Africa." Minerals 11, no. 6 (June 19, 2021): 651. http://dx.doi.org/10.3390/min11060651.

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Carbonaceous shale is more topical than ever before due to the associated unconventional resources of methane. The use of FTIR, SEM-EDX, and mineralogical analyses has demonstrated a promising approach to assess methanogenesis potentials in a more rapid and reliable manner for preliminary prospecting. Representative core samples from the borehole that penetrated the carbonaceous Mikambeni shale Formations were investigated for methanogenesis potentials. The absorption band stretches from 1650 cm−1 to 1220 cm−1 in wavenumber, corresponding to C-O stretching and OH deformation of acetic and phenolic groups in all studied samples, thereby suggesting biogenic methanogenesis. The CO2 was produced by decarboxylation of organic matter around 2000 cm−1 and 2300 cm−1 and served as a source of the carboxylic acid that dissolved the feldspar. This dissolution process tended to release K+ ions, which facilitated the illitization of the smectite minerals. The SEM-EDX spectroscopy depicted a polyframboidal pyrite structure, which indicated a sulfate reduction of pyrite minerals resulting from microbial activities in an anoxic milieu and causes an increase in alkalinity medium that favors precipitation of dolomite in the presence of Ca and Mg as burial depth increases. The contact diagenesis from the proximity of Sagole geothermal spring via Tshipise fault is suggested to have enhanced the transformation of smectite to chlorite via a mixed layer corrensite in a solid-state gradual replacement reaction pathway. The presence of diagenetic chlorite mineral is characteristic of low-grade metamorphism or high diagenetic zone at a temperature around 200 °C to 230 °C and corresponds to thermal breakdown of kerogen to methane at strong absorption band around 2850 cm−1 and 3000 cm−1, indicating thermal methanogenesis.

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Vasquez, Guilherme Fernandes, Marcio José Morschbacher, Camila Wense Dias dos Anjos, Yaro Moisés Parisek Silva, Vanessa Madrucci, and Julio Cesar Ramos Justen. "Petroacoustics and composition of presalt rocks from Santos Basin." Leading Edge 38, no. 5 (May 2019): 342–48. http://dx.doi.org/10.1190/tle38050342.1.

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The deposition of the presalt section from Santos Basin began when Gondwana started to break up and South America and Africa were separating. Initial synrift carbonate deposits affected by relatively severe tectonic activity evolved to a lacustrine carbonate environment during the later stages of basin formation. Although the reservoirs are composed of carbonate rocks, the occurrence of faults and the intense colocation of igneous rocks served as a source of chemical elements uncommon in typical carbonate environments. Consequently, beyond the presence of different facies with complex textures and pore geometries, the presalt reservoir rocks present marked compositional and microstructural variability. Therefore, rock-physics modeling is used to understand and interpret the extensive laboratory measurements of P-wave velocities, S-wave velocities, and density that we have undertaken on the presalt carbonate cores from Santos Basin. We show that quartz and exotic clay minerals (such as stevensite and other magnesium-rich clay minerals), which have different values of elastic moduli and Poisson's ratio as compared to calcite and dolomite, may introduce noticeable “Poisson's reflectivity anomalies” on prestack seismic data. Moreover, although the authors concentrate their attention on composition, it will become clear that pore-space geometry also may influence seismic rock properties of presalt carbonate reservoirs.

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Bau, Michael, Rolf L. Romer, Volker Lüders, and Nicolas J. Beukes. "Pb, O, and C isotopes in silicified Mooidraai dolomite (Transvaal Supergroup, South Africa): implications for the composition of Paleoproterozoic seawater and ‘dating’ the increase of oxygen in the Precambrian atmosphere." Earth and Planetary Science Letters 174, no. 1-2 (December 1999): 43–57. http://dx.doi.org/10.1016/s0012-821x(99)00261-7.

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Bezuidenhout, H., and G. J. Bredenkamp. "A reconnaissance survey of the vegetation of the dolomitic region in the Potchefstroom-Ventersdorp-Randfontein area, South Africa." Phytocoenologia 18, no. 2-3 (March 23, 1990): 387–403. http://dx.doi.org/10.1127/phyto/18/1990/387.

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Matthews, W. S., G. J. Bredenkamp, and N. van Rooyen. "The vegetation of the dry dolomitic regions of the north-eastern mountain sourveld of the Transvaal escarpment, South Africa." Phytocoenologia 20, no. 4 (July 9, 1992): 467–88. http://dx.doi.org/10.1127/phyto/20/1992/467.

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Buttrick, D. B., J. L. van Rooy, and R. Ligthelm. "Environmental geological aspects of the dolomites of South Africa." Journal of African Earth Sciences (and the Middle East) 16, no. 1-2 (January 1993): 53–61. http://dx.doi.org/10.1016/0899-5362(93)90161-i.

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Takai, Ken, Duane P. Moser, Mary DeFlaun, Tullis C. Onstott, and James K. Fredrickson. "Archaeal Diversity in Waters from Deep South African Gold Mines." Applied and Environmental Microbiology 67, no. 12 (December 1, 2001): 5750–60. http://dx.doi.org/10.1128/aem.67.21.5750-5760.2001.

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ABSTRACT A culture-independent molecular analysis of archaeal communities in waters collected from deep South African gold mines was performed by performing a PCR-mediated terminal restriction fragment length polymorphism (T-RFLP) analysis of rRNA genes (rDNA) in conjunction with a sequencing analysis of archaeal rDNA clone libraries. The water samples used represented various environments, including deep fissure water, mine service water, and water from an overlying dolomite aquifer. T-RFLP analysis revealed that the ribotype distribution of archaea varied with the source of water. The archaeal communities in the deep gold mine environments exhibited great phylogenetic diversity; the majority of the members were most closely related to uncultivated species. Some archaeal rDNA clones obtained from mine service water and dolomite aquifer water samples were most closely related to environmental rDNA clones from surface soil (soil clones) and marine environments (marine group I [MGI]). Other clones exhibited intermediate phylogenetic affiliation between soil clones and MGI in the Crenarchaeota. Fissure water samples, derived from active or dormant geothermal environments, yielded archaeal sequences that exhibited novel phylogeny, including a novel lineage ofEuryarchaeota. These results suggest that deep South African gold mines harbor novel archaeal communities distinct from those observed in other environments. Based on the phylogenetic analysis of archaeal strains and rDNA clones, including the newly discovered archaeal rDNA clones, the evolutionary relationship and the phylogenetic organization of the domain Archaea are reevaluated.

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Dippenaar, Matthys A., J. Louis van Rooy, and Roger E. Diamond. "Engineering, hydrogeological and vadose zone hydrological aspects of Proterozoic dolomites (South Africa)." Journal of African Earth Sciences 150 (February 2019): 511–21. http://dx.doi.org/10.1016/j.jafrearsci.2018.07.024.

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Eriksson, P. G., and W. Altermann. "An overview of the geology of the Transvaal Supergroup dolomites (South Africa)." Environmental Geology 36, no. 1-2 (November 20, 1998): 179–88. http://dx.doi.org/10.1007/s002540050334.

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Campbell-Young, G. J., and K. Balkwill. "A new species of Pearsonia (Fabaceae) from dolomites in Northern Province, South Africa." Nordic Journal of Botany 20, no. 5 (December 2000): 547–55. http://dx.doi.org/10.1111/j.1756-1051.2000.tb01602.x.

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Venter, I. S., and B. J. Gregory. "Risk assessment in dolomitic terrain: a case history." Geological Society, London, Engineering Geology Special Publications 4, no. 1 (1987): 329–34. http://dx.doi.org/10.1144/gsl.eng.1987.004.01.39.

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AbstractThe dewatering of dolomitic groundwater compartments in the Far West Rand in the Transvaal Province of South Africa has, in the past, resulted in ground movements in the form of subsidences and sinkholes. These have caused damage to various structures and in some instances loss of life. Dewatering of these compartments has taken place as a result of economic and safety considerations for the continued operation and development of deep-level gold mines in these areas. The dewatering of another groundwater compartment is currently underway. Consequently, a risk assessment, primarily to evaluate the potential for sinkhole development, was prepared for the main highways crossing the compartment.Risk assessment in dolomitic terrain is a much debated subject, the main reason being the subjectivity of the various approaches. It is generally accepted, however, that a number of factors affect subsurface stability, for example, the position of the watertable, the presence of weak, dolomitic residuum, bedrock characteristics and the ponding of surface-water. A combination of methods was utilized to produce a final assessment. These included a multivariate classification system and comparison with published data collated by the Geological Survey of South Africa. The methods and results of the risk assessment are discussed together with possible alternative solutions for maintaining the traffic routes and for ensuring the safety of road users.

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JORDAAN, MARIE, and ABRAHAM E. VAN WYK. "Gymnosporia sekhukhuniensis (Celastraceae), a new species from South Africa." Phytotaxa 408, no. 1 (June 27, 2019): 69–76. http://dx.doi.org/10.11646/phytotaxa.408.1.5.

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Gymnosporia sekhukhuniensis, a new species from north-eastern South Africa, is described, illustrated, mapped, and compared with closely related species. It belongs to Gymnosporia sect. Buxifoliae, more specifically Group 1, the members of which are characterized by the capsules being (2)3(4)-valved, rugose or verrucose, and the seeds partially covered by the aril. The new species has a restricted distribution range and is near-endemic to the Sekhukhuneland Centre of Endemism. This biogeographical region rich in restricted-range plants is more or less congruent with surface outcrops of mafic and ultramafic igneous rocks belonging to the Rustenburg Layered Suite of the eastern Bushveld Complex. The range of the new species shows marginal intrusion into the far northern part of the nearby Wolkberg Centre of Endemism, where it is associated with dolomites of the Malmani Subgroup. Gymnosporia sekhukhuniensis is a suffrutex mainly associated with rocky outcrops in open savannah. Diagnostic characters include its dwarf habit (up to 1.6 m tall), capsules that are relatively small (5–8 mm long), woody, scaly-rugose, with hard pointed apices, and leaves that are very laxly arranged on the stems, with some often present on the thorns. Also included is a key to the 10 currently accepted species in G. sect. Buxifoliae Group 1. The taxonomic significance of capsule and seed characters for demarcating sections and species in the genus Gymnosporia is emphasized.

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Humphreys, W. F., and Gary C. B. Poore. "First Record of Spelaeogriphacea From Australasia: a New Genus and Species From an Aquifer in the Arid Pilbara of Western Australia." Crustaceana 71, no. 7 (1998): 721–42. http://dx.doi.org/10.1163/156854098x00013.

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AbstractSpelaeogriphacea are reported for the first time from Australia. A new genus and species, Mangkurtu mityula, are described and the only other two genera diagnosed. The species, the third extant in the order, seems more similar to the Brazilian Potiicoara brasiliensis than to the South African Spelaeogriphus lepidops but all have unique apomorphies. The species is found in the aquifer in the Tertiary Millstream Dolomite of the Pilbara region of Western Australia. It is part of a fauna with clear Gondwanan affinities. This fauna is distinct from those found in aquifers in the lower and upper parts of the same drainage basin.

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Пхарое, Б. Л., and А. Н. Евдокимов. "Composition and provenance reconstruction of terrigenous deposits in the North-West of South Africa." Геология и геофизика Юга России, no. 4() (December 21, 2020): 124–49. http://dx.doi.org/10.46698/vnc.2020.48.31.008.

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Северо-западный регион ЮАР до недавнего времени не являлся промышленно марганценосным. Однако результаты изучения последних лет дают основание думать, что здесь могут быть залежи марганцевых руд. Марганцевое оруденение в этом регионе встречается в виде марганцевых конкреций, порошкообразного марганцевого вада и марганцевых корок в коре выветривания. Марганцевые конкреции приурочены к аллювиальной части «Westwits alluvium» рудного разреза и марганцевый вад накоплялся в карстовых структурах, образовавшихся в результате приповерхностного выветривания, выщелачивания и растворения подстилающих марганценосных неоархейских доломитов. Предполагается два потенциальных источника марганца: первый расположен непосредственно под рудным телом, а второй – на существенном удалении от него. Если первый источник рудного вещества поставлял марганец из подстилающих доломитов в процессе их выветривания, то второй вариант подразумевает существенный перенос металла из неизвестных коренных источников, расположенных на значительном удалении от области рудонакопления. Таким образом, для решения этого вопроса, необходимо провести экспериментальные исследования, изучающие природу, минералогию и источник сноса терригенных отложений «вмещающих материалов» верхнего рудного разреза. Цель работы – уточнить природу марганценосных терригенных залежей «Westwits alluvium» и, что самое важное, определить их коренной источник поступления и собственно минеральный состав. Методики исследования включали: петрографическое описание пород, геохимические анализы методами XRF и SEM, подсчеты объемного состава детритовых минералов и анализ дискриминационных диаграмм. Результаты. В результате проведенных исследований было установлено, что терригенные зёрна в основном представлены кварцем. Содержание полевых шпатов, минералов цемента и глинистых минералов не более 20 %. Использована классификация составов терригенного материала, основанная на подсчете в объемных процентах зерен кварца, полевого шпата, обломочных зерен других пород (вулканических, магматических и метаморфических пород), слюды и др. По этим данным были определены вероятные источники сноса, которыми являются породы Рэнд-Антиклинального хребта, расположенного к югу от изучаемого региона, а также архейские граниты, гнейсы и мафические-ультрамафические породы Каапваальского кратона. Осадконакопление происходило в низменной равнине с тропическим умеренно влажным и субгумидным климатом. Здесь, при повышенном рН воды происходило интенсивное выщелачивание пород и замещение детритовых зерен разного минерального состава диоксидом марганца. Ключевые слова: марганцовистый аллювий, третичный, терригенные отложения, Каапваальский кратон, Южная Африка The North-West region of the Republic of South Africa was previously not considered to constitute of manganese mineralization of industrial value. However, recently published articles indicated the presence of secondary manganese mineralization in the weathering crust, underlain by the manganiferous Neoarchean dolomites. Manganese mineralization in this region occurs in the form of manganese nodules, powdered manganese wad, and manganese crusts. Manganese nodules are confined to the alluvial part of the ore section known as the «Westwits alluvium» and manganese wad is accumulated in karstic structures formed as a result of near-surface weathering, leaching, and dissolution of underlying manganese-bearing Neoarchean dolomites. Two potential sources of manganese are assumed: the first relates to the dolomites which are located directly under the ore body, and the second relates to the source areas of terrigenous deposits. If the first hypothesis suggests that manganese ore substances were supplied from the underlying dolomites during their weathering, the second option then implies a significant transfer of metal from unknown root sources located at a considerable distance from the area of ore accumulation. Thus, it is necessary to conduct petrographic study to reconstruct their source regions and understand the close relations with Mn mineralization. Aim is to clarify the nature of the manganese-bearing terrigenous deposits «Westwits alluvium» and, most importantly, to determine their root source of supply and the actual mineral composition. Methodology of study includes mainly: petrographic study of rocks, geochemical analyses with the use of XRF and SEM methods, modal compositional analysis of the detrital minerals, and analysis of discrimination diagrams. Results. As a result of the conducted research, it was found that terrigenous grains consist mainly of detrital quartz grains. The content of feldspars, cement minerals and clay minerals seldom exceeds 20 %. The classification of terrigenous material based on the calculation of the volumetric percentage of the detrital framework grains: quartz, feldspar, clastic grains of other rocks types (volcanic, igneous and metamorphic rocks), mica, indicated probable source areas of the terrigenous sediments. These include metasedimentary rocks of the Rand Anticline Ridge which is located south of the studied region, and Archean granites, gneisses, and mafic-ultramafic rocks of the Kaapvaal Craton. In the basin of deposition, sedimentation occurred in a lowland plain within tropical region, characterized by moderately humid and sub-humid climatic conditions. These conditions, combined with oxidation and increased pH of the basin waters, contributed to the replacement of detrital grains with manganese dioxide

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Kaufmann, Lukas, Claudia Marcolli, Julian Hofer, Valeria Pinti, Christopher R. Hoyle, and Thomas Peter. "Ice nucleation efficiency of natural dust samples in the immersion mode." Atmospheric Chemistry and Physics 16, no. 17 (September 9, 2016): 11177–206. http://dx.doi.org/10.5194/acp-16-11177-2016.

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Abstract. A total of 12 natural surface dust samples, which were surface-collected on four continents, most of them in dust source regions, were investigated with respect to their ice nucleation activity. Dust collection sites were distributed across Africa, South America, the Middle East, and Antarctica. Mineralogical composition has been determined by means of X-ray diffraction. All samples proved to be mixtures of minerals, with major contributions from quartz, calcite, clay minerals, K-feldspars, and (Na, Ca)-feldspars. Reference samples of these minerals were investigated with the same methods as the natural dust samples. Furthermore, Arizona test dust (ATD) was re-evaluated as a benchmark. Immersion freezing of emulsion and bulk samples was investigated by differential scanning calorimetry. For emulsion measurements, water droplets with a size distribution peaking at about 2 µm, containing different amounts of dust between 0.5 and 50 wt % were cooled until all droplets were frozen. These measurements characterize the average freezing behaviour of particles, as they are sensitive to the average active sites present in a dust sample. In addition, bulk measurements were conducted with one single 2 mg droplet consisting of a 5 wt % aqueous suspension of the dusts/minerals. These measurements allow the investigation of the best ice-nucleating particles/sites available in a dust sample. All natural dusts, except for the Antarctica and ATD samples, froze in a remarkably narrow temperature range with the heterogeneously frozen fraction reaching 10 % between 244 and 250 K, 25 % between 242 and 246 K, and 50 % between 239 and 244 K. Bulk freezing occurred between 255 and 265 K. In contrast to the natural dusts, the reference minerals revealed ice nucleation temperatures with 2–3 times larger scatter. Calcite, dolomite, dolostone, and muscovite can be considered ice nucleation inactive. For microcline samples, a 50 % heterogeneously frozen fraction occurred above 245 K for all tested suspension concentrations, and a microcline mineral showed bulk freezing temperatures even above 270 K. This makes microcline (KAlSi3O8) an exceptionally good ice-nucleating mineral, superior to all other analysed K-feldspars, (Na, Ca)-feldspars, and the clay minerals. In summary, the mineralogical composition can explain the observed freezing behaviour of 5 of the investigated 12 natural dust samples, and partly for 6 samples, leaving the freezing efficiency of only 1 sample not easily explained in terms of its mineral reference components. While this suggests that mineralogical composition is a major determinant of ice-nucleating ability, in practice, most natural samples consist of a mixture of minerals, and this mixture seems to lead to remarkably similar ice nucleation abilities, regardless of their exact composition, so that global models, in a first approximation, may represent mineral dust as a single species with respect to ice nucleation activity. However, more sophisticated representations of ice nucleation by mineral dusts should rely on the mineralogical composition based on a source scheme of dust emissions.

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Evdokimov, Aleksandr, and Benedict Pharoe. "Features of the mineral and chemical composition of the Northwest manganese ore occurrence in the Highveld region, South Africa." Journal of Mining Institute 248 (May 25, 2021): 195–208. http://dx.doi.org/10.31897/pmi.2021.2.4.

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The Northwest manganese ore mineralisation is located at a relative distance from traditionally known manganese mining areas in a new manganese-bearing region (Highveld) in the Northwest Province, Republic of South Africa. The ore occurrence was studied on farms: Buchansvale 61 IQ, Weltevreden 517 JQ, Rhenosterhoek 343 JP and Kafferskraal 306 JP. The data obtained from studying the geology of the area pointed out to interests regarding the development criterias for search of similar ore mineralisations in the northwest region of South Africa. The ore occurs predominantly in the form of powdered manganese wad, manganese nodules and crusts, confined to the karstic structures of the upper section of the dolomites. X-ray powder diffraction (XRD), Scanning electron microscopy with energy dispersive link (SEM-EDS) and X-ray fluorescence were utilized to unveil the mineral and chemical composition of the ore samples. The present study therefore presents the results on both chemical and mineral composition of manganese ores, and their depth and longitudinal distribution. Karstic areas causing an increased local thickness of the ore body were identified. The geochemical and microspcopic study of the ores indicates their supergene nature. The main ore minerals includes cryptomelane, lithiophorite, purolusite, hollandite and romanechite associated with impurity components of Ba, Ce, Co, La, Cr, Zn and V.

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Van der Walt, I. J., and K. De Roer. "Hydrologic Impact of Rewatering of the Gemsbokfontein Dolomitic Western Subcompartment on the Wonderfonteinspruit, South Africa." Physical Geography 27, no. 4 (January 2006): 316–32. http://dx.doi.org/10.2747/0272-3646.27.4.316.

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Fairey, Brenton J., Martin J. Timmerman, Masafumi Sudo, and Harilaos Tsikos. "The Role of Hydrothermal Activity in the Formation of Karst-Hosted Manganese Deposits of the Postmasburg Mn Field, Northern Cape Province, South Africa." Minerals 9, no. 7 (July 3, 2019): 408. http://dx.doi.org/10.3390/min9070408.

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The Postmasburg Manganese Field (PMF), Northern Cape Province, South Africa, once represented one of the largest sources of manganese ore worldwide. Two belts of manganese ore deposits have been distinguished in the PMF, namely the Western Belt of ferruginous manganese ores and the Eastern Belt of siliceous manganese ores. Prevailing models of ore formation in these two belts invoke karstification of manganese-rich dolomites and residual accumulation of manganese wad which later underwent diagenetic and low-grade metamorphic processes. For the most part, the role of hydrothermal processes and metasomatic alteration towards ore formation has not been adequately discussed. Here we report an abundance of common and some rare Al-, Na-, K- and Ba-bearing minerals, particularly aegirine, albite, microcline, banalsite, sérandite-pectolite, paragonite and natrolite in Mn ores of the PMF, indicative of hydrothermal influence. Enrichments in Na, K and/or Ba in the ores are generally on a percentage level for most samples analysed through bulk-rock techniques. The presence of As-rich tokyoite also suggests the presence of As and V in the hydrothermal fluid. The fluid was likely oxidized and alkaline in nature, akin to a mature basinal brine. Various replacement textures, particularly of Na- and K- rich minerals by Ba-bearing phases, suggest sequential deposition of gangue as well as ore-minerals from the hydrothermal fluid, with Ba phases being deposited at a later stage. The stratigraphic variability of the studied ores and their deviation from the strict classification of ferruginous and siliceous ores in the literature, suggests that a re-evaluation of genetic models is warranted. New Ar-Ar ages for K-feldspars suggest a late Neoproterozoic timing for hydrothermal activity. This corroborates previous geochronological evidence for regional hydrothermal activity that affected Mn ores at the PMF but also, possibly, the high-grade Mn ores of the Kalahari Manganese Field to the north. A revised, all-encompassing model for the development of the manganese deposits of the PMF is then proposed, whereby the source of metals is attributed to underlying carbonate rocks beyond the Reivilo Formation of the Campbellrand Subgroup. The main process by which metals are primarily accumulated is attributed to karstification of the dolomitic substrate. The overlying Asbestos Hills Subgroup banded iron formation (BIF) is suggested as a potential source of alkali metals, which also provides a mechanism for leaching of these BIFs to form high-grade residual iron ore deposits.

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Van der Walt, I. J., and B. W. Richter. "The Effectiveness of Centre-Pivot Irrigation from Dolomitic Ground Water in the Northwest Province, South Africa." GeoJournal 61, no. 2 (2004): 197–201. http://dx.doi.org/10.1007/s10708-004-2888-z.

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Warke, Matthew R., Stefan Schröder, and Harald Strauss. "Testing models of pre-GOE environmental oxidation: A Paleoproterozoic marine signal in platform dolomites of the Tongwane Formation (South Africa)." Precambrian Research 313 (August 2018): 205–20. http://dx.doi.org/10.1016/j.precamres.2018.04.015.

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de Ruiter, Darryl J., and Lee R. Berger. "Leopards as Taphonomic Agents in Dolomitic Caves—Implications for Bone Accumulations in the Hominid-bearing Deposits of South Africa." Journal of Archaeological Science 27, no. 8 (August 2000): 665–84. http://dx.doi.org/10.1006/jasc.1999.0470.

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Mokoena, B. T., and J. P. Sebola. "A MULTI CRITERIA DECISION URBAN DEVELOPMENT FRAMEWORK FOR LAND EXPROPRIATION IN SOUTH AFRICA: A STRATEGIC APPROACH." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B4-2020 (August 25, 2020): 399–407. http://dx.doi.org/10.5194/isprs-archives-xliii-b4-2020-399-2020.

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Abstract. The land question in South Africa has been a long-standing issue for more than 360 years. Consequent to unjust legislation such as The Natives Land Act No.27 of 1913 to this day, there is a racial imbalance in the distribution of land ownership in South Africa. Coupled with the socio-economic and spatial segregative mandates of the apartheid-government to enrich the white minority, such unjust legislation fostered mass-land dispossessions and displacements of black people relocating them to peripheral areas known as ‘Bantu stands’ where they were further ethnically grouped in remote from socio-economic opportunities. The preceding has resulted in the impoverishment of the black people as they no longer had land – their primary source of livelihood. The limited access to land by black people remains true in post-apartheid South Africa.Since the dawn of democracy, limited access to urban land has coursed challenges for housing development. Spatial transformation towards socio-economic integration has also become problematic as large areas of strategically located land remain locked in the hands of the minorities. Thus, to realise the mandates of South Africa’s democratic government – equal access to land and opportunities, this land needs to be acquired, particularly for the previously disadvantaged, poor, and landless.As cities move towards being smart, this research will demonstrate the use of Evidence Based Planning (EBP) in order to assist Local Government to foster scientific decision making methods. The use of the Multi-Criteria Decision Analysis (MCDA), Analytical Hierarchy Process (AHP) and Geographic Information System (GIS) as a method to develop a Strategic Urban Development Decision Framework (SSUDDF) as a Planning Support System (PSS) that will be used to investigate the best suitable land for possible expropriation. Various criteria such as proximity to road connectivity, proximity to current and future economic activity, proximity to public transport routes, dolomitic land, priority areas and proximity to city centres are some of the criteria selected for the research. The Strategic Spatial Urban Development Decision Framework (SSUDDF) enabled us to stream line significant criteria and processes that where specific to strategic urban development in the Benoni town situated in the City of Ekurhuleni using critical spatial policy and strategic objectives of the city.

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Selebalo, Itumeleng M., Mary C. Scholes, and Jai K. Clifford-Holmes. "A Systemic Analysis of the Environmental Impacts of Gold Mining within the Blyde River Catchment, a Strategic Water Area of South Africa." Water 13, no. 3 (January 26, 2021): 301. http://dx.doi.org/10.3390/w13030301.

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Exploratory modelling of the impact of gold mining on groundwater in a strategic water area of South Africa was undertaken. A systems dynamics (SD) model was developed to simulate the impact of gold mining on water quality, focusing on groundwater contamination risk, within the context of competing developmental priorities around water resource development and the socio-economic gains from gold mining. The model also identified interventions to minimise the impacts by the year 2040. The study area was the Blyde River Catchment (BRC), which is part of the Olifants Water Management Area in South Africa. This area is an important contributor, currently and in the future, to freshwater flows and groundwater in the Olifants River Catchment, which is one of South Africa’s most economically important catchments. The model development process included a causal loop diagram–based problem conceptualisation, followed by the drawing of stock-flow diagrams and the determining of model parameters based on a combination of background literature, data from environmental impact assessments, and from the national Department of Water and Sanitation. The model showed the potential environmental risks of gold mine wastewater production and interventions to minimise these risks. The most effective intervention identified to reduce the risk of groundwater contamination was the development and use of synthetic-lined tailings dams. The baseline simulation result of sulphate loading of 5430 t/year can be reduced by 3070 t/year to give a simulated sulphate load of 2270 t/year in 2040 using this intervention. In comparison, the simulated wastewater recycling intervention only reduced the sulphate load to 4630 t/year and the wastewater treatment interventions to 3420 t/year. This project contributes to the exploratory modelling of an understudied region of the Olifants River Catchment that is a crucial provider of freshwater flows to the Olifants, which is threatened by increasing gold mining in the upper BRC. The SD model highlighted the importance of protecting the dolomitic aquifers in the BRC for the long term sustainability of the catchment, which is particularly important if groundwater development occurs.

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Smith, Gideon F., and Estrela Figueiredo. "Kalanchoe crouchii Gideon F.Sm. & Figueiredo (Crassulaceae), a New Species from the Dolomites of the Wolkberg Centre of Endemism, Mpumalanga Province, South Africa." Haseltonia 2018, no. 25 (December 28, 2018): 84. http://dx.doi.org/10.2985/026.025.0107.

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Manzi, Musa S. D., Raymond J. Durrheim, Kim A. A. Hein, and Nick King. "3D edge detection seismic attributes used to map potential conduits for water and methane in deep gold mines in the Witwatersrand basin, South Africa." GEOPHYSICS 77, no. 5 (September 1, 2012): WC133—WC147. http://dx.doi.org/10.1190/geo2012-0135.1.

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Inrushes of ground water and the ignition of flammable gases pose risks to workers in deep South African gold mines. Large volumes of water may be stored in solution cavities in dolomitic rocks that overlie the Black Reef (BLR) Formation, while there are several possible sources for methane, namely, coal seams, kerogen found in some gold ore bodies, or methane introduced by igneous intrusions. Potential conduits that may transport water and methane to underground workings were mapped using 3D reflection seismic data. Edge detection attributes successfully identified many faults, some with displacements as small as 10 m. Faults that displace the Ventersdorp Contact Reef (VCR) and the BLR horizons were of special interest, as known occurrences of fissure water and methane in underground workings show a good correlation with faults that were imaged on the VCR and BLR horizons. Because there are uncertainties in determining the linkage of faults with aquifers and methane sources, it is considered prudent to assume that all structures that displace the VCR and BLR horizons are potential conduits.

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Winde, Frank. "Challenges for Sustainable Water Use in Dolomitic Mining Regions of South Africa—A Case Study of Uranium Pollution Part I: Sources and Pathways." Physical Geography 27, no. 4 (January 2006): 333–47. http://dx.doi.org/10.2747/0272-3646.27.4.333.

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Journal articles on the topic 'Dolomite - South Africa'

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